SEOUL -- Lee Jae-myung, former chief of South Korea's Democratic Party, was elected presidential candidate for the liberal party overwhelmingly, the party said Sunday.

Lee won 89.77 percent of all votes cast in the party's primary, marking the highest ever recorded in the Democratic Party-affiliated primaries since the country's democratization in 1987.

The human rights lawyer-turned-politician was followed by Kim Dong-yeon, Gyeonggi province governor, with 6.87 percent, and Kim Kyung-soo, former governor of South Gyeongsang province, with 3.36 percent.

With the overwhelming primary victory, Lee cemented his position as a presidential frontrunner in the election scheduled for June 3, triggered by the ouster of President Yoon Suk-yeol from office over his botched martial law imposition last December.

Lee, who lost the 2022 presidential election to Yoon by the country's narrowest margin of 0.73 percentage points, has been seen as the most powerful contender for the upcoming election.

Last week's Gallup Korea poll showed that Lee came out on top with a support rate of 38 percent, taking a big lead over conservative presidential hopefuls.

Lee's support rate has hovered above 30 percent since December last year when Yoon declared an emergency martial law on the night of Dec. 3, which was revoked by the opposition-led National Assembly hours later.

The poll showed that 45 percent will vote for a presidential candidate of the Democratic Party, while 32 percent will give their vote to a candidate of the conservative People Power Party.